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AZURITE MINE REMOVAL ACTION OVERVIEW. Dustin G. Wasley, PE, Principal – CES 2013 American Society of Mining and Reclamation Conference Laramie, Wyoming -- June 6, 2012. Azurite Mine Overview. Abandoned Underground Gold Mine, Located in North-Central WA on USFS-Administered Land

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AZURITE MINE REMOVAL ACTION OVERVIEW

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AZURITE MINEREMOVAL ACTION OVERVIEW

Dustin G. Wasley, PE, Principal – CES

2013 American Society of Mining and Reclamation Conference

Laramie, Wyoming -- June 6, 2012


Azurite Mine Overview

  • Abandoned Underground Gold Mine, Located in North-Central WA on USFS-Administered Land

  • Northwest of Mazama, Near Harts Pass Recreation Area & Pacific Crest Trail

  • Remote with Poor Access, Steep Terrain

  • Several RTE Species – Aquatic and Terrestrial

  • Inventoried Roadless/Non-Motorized Management Area

  • High Value for Potential Wilderness Area in Future


Azurite Mine Location

AZURITE MINE

MAZAMA


OVERVIEW OF AZURITE MINE FROM TINSON ADIT

TAILINGS

~55,000 CY

~4 acres

CADY PASS

MILL AREA

WASTE ROCK

~22,000 CY

~1 acre

WENATCHEE ADIT

MILL CREEK

OFFICE BUILDING


Azurite Mine – Early History

  • 1915 – 31 Claims Staked

  • 1916 – Azurite Copper Company (renamed Azurite Gold)

  • 1918 to 1931 – Underground Development

  • 1934 – ASARCO Leased Mine

  • 1934 to 1936 – 100 TPD Mill and Infrastructure

  • 1936 to 1942 –Development, Production

    • ~73,000 tons @ 0.38 opt gold

  • 1942 – ASARCO Removes Equipment


Historic Photos - 1936


Azurite Mine – Recent History

  • 1995 – Discovery Assessment (USFS)

  • 2002 – IAM Open File Report (WA DNR)

  • 2004/2005 – CERCLA Site Inspection (USFS/CES)

  • 2005 – Reprocessing Study (USFS/CES); – PRP Report (USFS)

  • 2006 to 2008 – EE/CA & Risk Assessment (ASARCO/MFG)

  • 2008 – ASARCO Settlement with USFS~$5.5M

  • 2007 to 2010 – Data Gaps/Removal Design (USFS/CES)

  • 2011 – Removal Action Activities


Final Removal Action Alternative

  • Access Road Improvements / Bridge Replacement (2010)

  • Temporary Access Road Across Mill Creek (2011)

  • Mill Creek Diversion Away from Waste Rock Pile (2011)

  • Onsite Covered Repository (2011)

    • Reinforced Stabilized Slope/Repository Toe Berm

    • Waste Rock and Mill Area Soil Blended with Tailings

    • Multi-Layer Cover, HDPE Membrane, and Talus/Rock Cover

  • Physical Hazard Closures (2011)

  • Revegetation (2011) – USFS Lead


Construction Challenges

  • Weather Conditions (rain, snow, heat)


Construction Challenges

  • Weather Conditions (rain, snow, heat)

  • Typical Construction Window (late June – early October)

  • Steep Slopes / Difficult Terrain

  • Limited Onsite Staging Areas

  • All Borrow Material from Onsite

  • Remote Access/Logistics/Communication


2011 Removal Action Summary

  • Turnkey “Design/Build” Contract Structure

    • CES – Prime Contractor

    • Palm Construction – Main Subcontractor (Local)

  • Mobilization – July 11, 2011 – 3 weeks late (weather)

  • Continuous Work Schedule, CES and Subs

  • Demobilization – September 26, 2011 – 1 week early


OVERVIEW OF AZURITE MINE REMOVAL ACTION

TAILINGS PILE

Contour with WR/Mill Soils, and Construct Repository

STABILIZED SLOPE

Construct to retain Repository

WASTE ROCK

Excavate and Haul to Repository

MILL AREA

Excavate and Haul to Repository


Camp, Equipment and Manpower

  • Remote Camp (internet, phones, running water, flushing toilets, showers, washer/dryer, cook, tents/campers)

  • 3 Excavators

  • 2 Loaders

  • 3 Dozers

  • 2 Off-Road, Articulated Haul Trucks

  • Roller Compactor, Water Truck, Misc. Work Trucks

  • Bear Proof Storage Containers

  • Manpower – 10 to 20 (Palm/Subs) / 1 to 3 (CES)


Erosion and Sediment Control

  • Run-On Ditches

    • Waste Rock / Tailings

  • Silt Fence

    • Borrow Area / Waste Rock

  • Filter Berms

    • Borrow Area / Waste Rock

  • Sedimentation Pond

    • Tailings / Repository


Mill Creek Crossing and Diversion

  • Access Waste Rock Pile, and Transport to Repository

  • Three, 48-inch CMPs

  • Temporarily Divert Mill Creek Away From Waste Rock Pile


Mill Creek Crossing


Borrow Area Development

  • Onsite Source for Screening / 3 Products

  • 2-inch minus

    • Stabilized Slope Fill, Road Bed/Base, Fill Material

    • 40,000+ cubic yards used, more remains onsite

  • 2-inch to 36-inch

    • Repository cover, rocked diversion ditches

    • ~20,000 cubic yards

  • 36-inch plus

    • Misc. Placement, armoring


Borrow Area Development


Borrow Area Development


Underground Working Closures

  • Planned for 5 Closures (4 Adits / 1 Vent)

  • Pre-Cut Steel and Culverts Delivered to Site

  • Final Onsite Fabrication

  • Installation with Helicopter and Onsite Welder

  • 4 Closures

    • Burnham, Tinson, and Discovery Adits

    • Discovery Vent

  • Wenatchee Adit

    • Collapsed - No Bat Gate Installed


Reinforced Stabilized Slope

  • Designed to Stabilize/Retain the Repository

  • Original Design was 15-feet (H) x 15-feet (W) – 12 lifts

  • Final Layout was 22-feet (H) x 25-feet (W) – 17 lifts

    • Competent Soil Deeper Than Planned

    • Increased Quantities For Borrow Material/Geogrid

  • Onsite QA/QC Testing – All Final Tests Met Compaction Requirements (95% of Proctor)

  • 23 days to build

    • Bottom lifts ~ 1.5 days to complete

    • Upper lifts ~ 1 day to complete


Reinforced Stabilized Slope Typical


Reinforced Stabilized Slope – Lift 1


Reinforced Stabilized Slope – Lift 4


Reinforced Stabilized Slope – Lift 8


Reinforced Stabilized Slope – Lift 12


Reinforced Stabilized Slope – Lifts 14/15


Reinforced Stabilized Slope – Complete


Waste Rock Excavation and Placement

  • Design Estimate was 22,000 bcy of Waste Rock

  • Risk Assessment Cleanup Goal – 104 mg/kg Total Arsenic

  • Revised Cleanup Goal – 204 mg/kg Total Arsenic

    • Additional Background Soil Sampling

    • Used MTCA Stat 3.0 to Calculate Natural Background

  • In-Field Screening with Niton XRF (RPDs ≤ 33%)

  • Final Quantities ~ 16,500 bcy


Waste Rock Pile – Before


Waste Rock Pile – Removal


Waste Rock Pile – Removal


Waste Rock Pile – Final


Onsite Repository

  • Overall Slope = 2.5:1

  • Reinforced Slope and Berm to Stabilize Repository

  • Waste Rock Blended with Tailings to Achieve Slope

  • In-sloped Benches Every 9 Vertical Feet

  • Repository Cover (Multi-Layer)

    • Talus/Rock Cover – Top

    • Geogrid

    • 12-oz Nonwoven Geotextile

    • 40-mil HDPE Membrane

    • 12-oz Nonwoven Geotextile

    • Waste Rock/Tailings – Bottom


Repository Grading Plan


Repository Cross Section Detail


Tailings Pile - Before


Tailings Pile - Before


Tailings Pile – Oxidation Profile


Repository Benching / Grading


Repository Benching / Grading


Repository Benching / Grading


Liner Installation


Liner Layers


Liner Installation


Liner Installation


Liner / Cover Installation


Repository – Final


Repository – Final


Repository / Tailings Pile – Before


Repository – Final


Summary

  • Completed 4 Weeks Ahead of Schedule

  • Field Changes Easily Made with Continuous Oversight & Communication

  • No Health/Safety Concerns

  • 3-Years of Long-term O&M Inspections, & Monitoring

  • RA Cost - $2.5M Capital


QUESTIONS


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